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    SubjectRe: [PATCH RFC 5/7] perf pmu: Support matching by sysid
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    On 11/02/2020 13:47, Jiri Olsa wrote:

    Hi Jirka,

    >>>> +
    >>>> + return buf;
    >>>> +}
    >>>> +
    >>
    >> I have another series to add kernel support for a system identifier sysfs
    >> entry, which I sent after this series:
    >>
    >> https://lore.kernel.org/linux-acpi/1580210059-199540-1-git-send-email-john.garry@huawei.com/
    >>
    >> It is different to what I am relying on here - it uses a kernel soc driver
    >> for firmware ACPI PPTT identifier. Progress is somewhat blocked at the
    >> moment however and I may have to use a different method:
    >>
    >> https://lore.kernel.org/linux-acpi/20200128123415.GB36168@bogus/
    >
    > I'll try to check ;-)

    Summary is that there exists an ACPI firmware field which we could
    expose to userspace via sysfs - this would provide the system id.
    However there is a proposal to deprecate it in the ACPI standard and, as
    such, would prefer that we don't add kernel support for it at this stage.

    So I am evaluating the alternative in the meantime, which again is some
    firmware method which should allow us to expose a system id to userspace
    via sysfs. Unfortunately this is arm specific. However, other archs can
    still provide their own method, maybe a soc driver:

    Documentation/ABI/testing/sysfs-devices-soc#n15

    >
    >>
    >>>> +static char *perf_pmu__getsysid(void)
    >>>> +{
    >>>> + char *sysid;
    >>>> + static bool printed;
    >>>> +
    >>>> + sysid = getenv("PERF_SYSID");
    >>>> + if (sysid)
    >>>> + sysid = strdup(sysid);
    >>>> +
    >>>> + if (!sysid)
    >>>> + sysid = get_sysid_str();
    >>>> + if (!sysid)
    >>>> + return NULL;
    >>>> +
    >>>> + if (!printed) {
    >>>> + pr_debug("Using SYSID %s\n", sysid);
    >>>> + printed = true;
    >>>> + }
    >>>> + return sysid;
    >>>> +}
    >>>
    >>> this part is getting complicated and AFAIK we have no tests for it
    >>>
    >>> if you could think of any tests that'd be great.. Perhaps we could
    >>> load 'our' json test files and check appropriate events/aliasses
    >>> via in pmu object.. or via parse_events interface.. those test aliases
    >>> would have to be part of perf, but we have tests compiled in anyway
    >>
    >> Sorry, I don't fully follow.
    >>
    >> Are you suggesting that we could load the specific JSONs tables for a system
    >> from the host filesystem?
    >
    > I wish to see some test for all this.. I can only think about having
    > 'test' json files compiled with perf and 'perf test' that looks them
    > up and checks that all is in the proper place

    OK, let me consider this part for perf test support.

    Thanks,
    John

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